Mineral resembling coal (3)

I believe the answer is:

jet

I believe this clue is a double definition.

'mineral' is the first definition.
(jet is a kind of mineral)

'coal' is the second definition.
(thesaurus)

'resembling' acts as a link.

(Other definitions for jet that I've seen before include "Black gemstone" , "Sort of black" , "Jumbo plane?" , "The blackest black" , "Rapid stream of liquid or gas" .)

I've seen this clue in the Evening Standard.

Want a hint initially instead of a full solution? Install my app